Dithering must be the last step in the Mastering Process.
It usually is needed when reducing bit-depth
For example: from 24 bit used in the mixing process to 16 bit CD standard.
Choosing the right type of dither for a special program material is a very complex task
and it demands some experience. Please do not use dithering in your mix
I will do this for you during CD Authoring.
When in doubt I recommend contacting me to talk about exceptional dithering situations.

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